Multi-beam scanning device, multi-beam scanning method, light source device, and image forming apparatus

A light source device for use in a multi-beam scanning device, the light source device comprising:

• a semiconductor laser array having a plurality of light emitting parts emitting multiple laser beams;
• a coupling lens coupling the laser beams emitted by the laser array;
• and
• an aperture stop restricting a diameter of the laser beams passed through the coupling lens,
• wherein the multi-beam scanning device comprising:
• the light source device;
• a rotary deflector deflecting the laser beams emitted by the light emitting parts of the laser array;
• and
• a focusing optical system focusing the deflected laser beams from the rotary deflector onto a scanned surface to form a plurality of beam spots that are separated on the scanned surface in a sub-scanning direction, the scanned surface being scanned simultaneously with the plurality of beam spots in a main scanning direction by a rotation of the rotary deflector,
• wherein the laser array is configured such that the light emitting parts are arrayed along a line that is at an inclination angle φ to the sub-scanning direction, the inclination angle φ measured in degrees and meeting the condition 0≦0<90, and that a scanning line pitch P, an array pitch ρ of the light emitting parts of the laser array and a parameter K defined by the equation K=0.82 λ/ωz, where λ is a wavelength of the emitted laser beams and ωz is a target beam spot diameter in the sub-scanning direction, satisfy the following conditions:
• 0.01<K·P/(ρ·cos φ)<0.30 0.011<K<0.030
• and wherein the aperture stop is configured to have a numerical aperture NAzS in the sub-scanning direction that satisfies the conditions:
• 0.01<NAzS<0. 30.

A multi-beam scanning method comprising the steps of:

• providing a semiconductor laser array having a plurality of light emitting parts emitting multiple laser beams;
• providing a rotary deflector deflecting the laser beams emitted by the light emitting parts of the semiconductor laser array;
• focusing the deflected laser beams from the rotary deflector onto a scanned surface to form a plurality of beam spots that are separated on the scanned surface in a sub-scanning direction;
• and
• scanning the scanned surface simultaneously with the plurality of beam spots in a main scanning direction by a rotation of the rotary deflector;
• wherein the laser array is configured such that the light emitting parts are arrayed along a line that is at an inclination angle φ to the sub-scanning direction, the inclination angle φ measured in degrees and meeting the conditions 0≦φ<90, and that a scanning line pitch P, an array pitch ρ of the light emitting parts of the laser array and a parameter K defined by the equation K=0.82 λ/ωz, where λ is a wavelength of the emitted laser beams and ωz is a target beam spot diameter in the sub-scanning direction, satisfy the following conditions:
• 0.01<K·P/(ρ·cos φ)<0.30 0.011<K<0.030.

An image forming apparatus in which a multi-beam scanning device is provided, the image forming apparatus forming an electrostatic latent image on a scanned surface of a photosensitive medium through an exposure of the photosensitive medium to an imaging light pattern provided by the multi-beam scanning device, the multi-beam scanning device comprising:

• a semiconductor laser array having a plurality of light emitting parts emitting multiple laser beams;
• a rotary deflector deflecting the laser beams emitted by the light emitting parts of the semiconductor laser array;
• and
• a focusing optical system focusing the deflected laser beams from the rotary deflector onto a scanned surface to form a plurality of beam spots that are separated on the scanned surface in a sub-scanning direction, the scanned surface being scanned simultaneously with the plurality of beam spots in a main scanning direction by a rotation of the rotary deflector,
• wherein the laser array is configured such that the light emitting parts are arrayed along a line that is at an inclination angle φ to the sub-scanning direction, the inclination angle φ measured in degrees and meeting the conditions 0≦φ<90, and that a scanning line pitch P, an array pitch ρ of the light emitting parts of the laser array and a parameter K defined by the equation K=0.82 λ/ωz, where λ is a wavelength of the emitted laser beams and ωz is a target beam spot diameter in the sub-scanning direction, satisfy the following conditions:
• 0.01<K·P/(ρ·cos φ)<0.30 0.011<K<0. 030.

A multi-beam scanning device comprising:

• semiconductor laser array means having a plurality of light emitting parts for emitting multiple laser beams;
• rotary deflector means for deflecting the laser beams emitted by the light emitting parts of the laser array means;
• and
• focusing optical means for focusing the deflected laser beams from the rotary deflector means onto a scanned surface to form a plurality of beam spots that are separated on the scanned surface in a sub-scanning direction, the scanned surface being scanned simultaneously with the plurality of beam spots in a main scanning direction by a rotation of the rotary deflector means,
• wherein the laser array means is configured such that the light emitting parts are arrayed along a line that is at an inclination angle φ to the sub-scanning direction, the inclination angle φ measured in degrees and meeting the conditions 0≦φ<90, and that a scanning line pitch P, an array pitch ρ of the light emitting parts of the laser array means and a parameter K defined by the equation K=0.82 λ/ωz, where λ is a wavelength of the emitted laser beams and ωz is a target beam spot diameter in the sub-scanning direction, satisfy the following conditions:
• 0.01<K·P/(ρ·cos φ)<0.30 0.011<K<0. 030.